In various types of valves, i.e. double seat valves also known as mix proof valves, it is commonly known to clean a valve seat by circulating cleaning liquid through said open valve seat. The cleaning is done for hygienic reasons and is normally done in an automatic manner with a certain time interval or the like.
The valve can be cleaned with the valve seat fully open but the cleaning is mainly done with a partly open valve seat to minimize the amount of used cleaning liquid and at the same time a partly open valve seat also has the advantage that a flow of cleaning liquid is flushed through at the exact place that is to be cleaned. The valve seat to be cleaned can be positioned in-stream or end-stream.
A double seat valve—for instance—typically has an upper and a lower valve part and the specific primary valve parts are each centred with at least a gasket and a guide band. These parts are situated with a small distance and create a sealing between the housing and the stem connected to the valve part. During operation of the valve said gasket can and will be exposed to the medium flowing through the valve and thus the gasket and the guide band have to be cleaned due to hygienic demands.
In the known solutions such a cleaning has to be done by taking the valve apart or by a manual cleaning, where only the stem and the outer surfaces of the parts are cleaned, leaving the area between the gasket and the guide band in a somewhat unclean state.